This invention relates to the manufacture of shingles, such as roofing shingles, and in particular, to shingles having granules of a background color and blend drops of granules of various shades of colors that are different from the background color. More particularly, this invention pertains to a method of monitoring the color of various portions of the shingle.
Asphalt-based roofing materials, such as roofing shingles, roll roofing and commercial roofing, are installed on the roofs of buildings to provide protection from the elements, and to give the roof an aesthetically pleasing look. Typically, the roofing material is constructed of a substrate such as a glass fiber mat or an organic felt, an asphalt coating on the substrate, and a surface layer of granules embedded in the asphalt coating.
A common method for the manufacture of asphalt shingles is the production of a continuous sheet of asphalt material followed by a shingle cutting operation which cuts the material into individual shingles. In the production of asphalt sheet material, either a glass fiber mat or an organic felt mat is passed through a coater containing hot liquid asphalt to form a tacky, asphalt coated sheet. Subsequently, the hot asphalt coated sheet is passed beneath one or more granule applicators which discharge protective and decorative surface granules onto portions of the asphalt sheet material.
In the manufacture of colored shingles, two types of granules are typically employed. Headlap granules are granules of relatively low cost used for the portion of the shingle that will be covered up on the roof. Colored granules or prime granules are of relatively higher cost and are applied to the portion of the shingle that will be exposed on the roof.
To provide a color pattern of pleasing appearance, the colored portion of the shingles may be provided with areas of different colors. Usually the shingles have a background color and a series of granule deposits of different colors or different shades of the background color. A common method for manufacturing the shingles is to discharge blend drops onto spaced areas of the tacky, asphalt coated sheet. Background granules are then discharged onto the sheet and they adhere to the tacky, asphalt coated areas of the sheet between the granule deposits formed by the blend drops. The term xe2x80x9cblend dropxe2x80x9d, as used herein, refers to the flow of granules of different colors or different shades of color (with respect to the background color) that is discharged from a granule blend drop applicator onto the asphalt coated sheet. The patch or assemblage of the blend drop granules on the asphalt coated sheet is also referred to as the xe2x80x9cblend dropxe2x80x9d.
The apparatus for depositing granules onto the asphalt coated sheet is referred to as a blender, which can be comprised of a series of hoppers positioned to drop granules onto the sheet. In a typical blend drop shingle operation, the blender includes four hoppers that periodically deposit blend drops of granules of four different shades. The blender also includes a fifth hopper that drops background granules on the areas of the asphalt coated sheet that have not been covered by granules from the first four hoppers.
Various types of granule dispensing hoppers are known for use in granule blenders. One type of dispensing hopper is a fluted roll. Another type is a pneumatically assisted and controlled hopper as disclosed in U.S. Pat. No. 5,520,889 to Burton et al. Since the manufacture of shingles is carried out at high continuous line speeds of hundreds of feet per minute, coordination and timing for the granule deposits from the various hoppers is imperative. The blender is usually operated by an electronic blender controller that provides signals to the various granule hoppers to impart the proper sequencing and duration of the blend drops of each blend drop color, and of the background color.
The various shades or colors in each of the hoppers are typically created by mixing colored granules of different colors from several different supplies of granules, each of which is a pure or single color. For example, the first blend drop may be made by mixing three parts pure brown granules and one part pure black granules. The second blend drop may be made by mixing four parts pure brown granules and two parts pure white granules. Other combinations may be used for the third and fourth blend colors. The fifth hopper may contain background granules that are a color reflecting a combination of the granules from the first four hoppers.
One of the problems associated with the manufacture of shingles with blend drops is that the shade or color can deviate from the designed shade or color, and therefore be out of specification. This can occur because of incomplete mixing of the granules, or from a malfunction of the blender or the hopper for that particular blend drop. Deviations from the desired shade can also occur because of operator error associated with measuring and combining the granules for the blends from the original supplies of pure-colored granules. Sometimes defects or variations in shades or colors cannot be detected during the manufacturing of the shingles. In such cases the defect may not be discovered until the shingles are actually installed on a roof. It would be advantageous if there could be developed a method for monitoring the color of the various blend drops during the shingle manufacturing process.
The above objects as well as other objects not specifically enumerated are achieved by a method of producing asphalt strip shingles including depositing blend drops of blend drop granules onto an asphalt coated sheet, sensing the color of the blend drops; comparing the sensed color of the blend drops with a reference color, and providing a signal indicative of the comparison.
According to this invention, there is also provided a method of producing asphalt strip shingles including continuously coating a substrate with asphalt to form an asphalt coated sheet, moving the asphalt coated sheet in a machine direction, depositing blend drops of blend drop granules onto the asphalt coated sheet from a blender, providing a signal indicative of the presence of the blend drops at a location downstream from the blender, sensing the color of the blend drops at the downstream location with a sensor, comparing the sensed color of the blend drops with a reference color, and providing a signal indicative of the comparison.
According to this invention, there is also provided a method of producing asphalt strip shingles including making shingles of a first color on a shingle machine including programming a controller with a reference color, depositing blend drops of blend drop granules onto an asphalt coated sheet, sensing the color of the blend drops, comparing the sensed color of the blend drops with the reference color, and providing a signal indicative of the comparison. The shingle machine is switched to make shingles of another color. Then the shingle machine is switched back to again make shingles of the first color, using the programmed reference color for comparing the color of the blend drops.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.